18 Sextantis

18 Sextantis (HD 88333; HR 3996; 32 G. Sextantis), or simply 18 Sex, is a solitary star^[15] located in the southern constellation Sextans. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.62.^[2] Gaia DR3 parallax measurements imply a distance of 558 light-years^[1] and it is slowly receding with a poorly constrained heliocentric radial velocity of approximately 0.2 km/s.^[5] At its current distance, 18 Sex's brightness is diminished with an interstellar extinction of two-tenths of a magnitude^[16] and it has an absolute magnitude of −0.16.^[6]

ConstellationSextans

Right ascension10^h 10^m 55.86074^s[1]

Declination−08° 25′ 06.4527″^[1]

Apparentmagnitude(V)5.62±0.01^[2]

Quick facts Constellation, Right ascension ...

18 Sextantis

Location of 18 Sex on the map (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Sextans
Right ascension	10h 10m 55.86074s[1]
Declination	−08° 25′ 06.4527″[1]
Apparent magnitude (V)	5.62±0.01[2]
Characteristics
Spectral type	K2/3 III[3]
U−B color index	+1.42[4]
B−V color index	+1.30[4]
Astrometry
Radial velocity (Rv)	0.2±2.9[5] km/s
Proper motion (μ)	RA: âˆ’0.115 mas/yr[1] Dec.: âˆ’43.987 mas/yr[1]
Parallax (π)	5.8416±0.0881 mas[1]
Distance	558 ± 8 ly (171 ± 3 pc)
Absolute magnitude (MV)	−0.16[6]
Details
Radius	27.3±1.4[7] R☉
Luminosity	222±12[8] L☉
Surface gravity (log g)	1.72[9] cgs
Temperature	4,410±122[10] K
Metallicity [Fe/H]	−0.31+0.01 −0.00[11] dex
Rotational velocity (v sin i)	<1.0[12] km/s
Other designations
18 Sex, 32 G. Sextantis[13], BD−07°2977, GC 13990, HD 88333, HIP 49865, HR 3996, SAO 137395, TIC 26206896[14]
Database references
SIMBAD	data

Close

18 Sex has a stellar classification of K2/3 III,^[3] indicating that it is an evolved star with the characteristics of a K2 and K3 giant star. At present, it has exhausted hydrogen at its core and it has expanded to 27.3 times the radius of the Sun.^[7] It radiates 222 times the luminosity of the Sun^[8] from its enlarged photosphere at an effective temperature of 4,410 K.^[10] Gaia DR3 models it to be a larger and brighter red giant branch star with a radius of 35.27 R_☉ and a luminosity of 384 L_☉.^[1] 18 Sex is metal deficient with an iron abundance of [Fe/H] = −0.31 or 49% of the Sun's^[11] and it spins too slowly for its projected rotational velocity to be measured accurately, having a velocity lower than 1.0 km/s.^[12]